Variable condenser



June 2, 1936. M, OSNOS 2,042,957

VARIABLE CONDENSER Filed June 17, 1932 f INVENTOR MENDEL OSNOS ATI'ORNEY enema am 2, i936 TED STATES VARIABLE CONDENSER Mendel Osnos, Berlin, Germany, 1 assignor to Telefunken Ggselischaft fiir Drahtlose Telegraphic m. b. 11., Berlin, Germany, a corporation of Germany Application June 17, 1932, Serial No. 617,762 In Germany June 29, 1931 9 Claims. (Cl. 175-- 41.5)

For the purpose ofproducing the wobbling of a transmitted signal it has heretofore been cu'stomary to use condensers with mechanical means for varying the capacity. However, this mechanical variation in most cases is attended with difflculties. Another fact is that the mechanical means of variation is not always adjustable with adequate reliability and delicacy.

According to the present invention the signal wobbling action is produced by the proper regulation ofithe required transmitting apparatus by thermal means, forlnstance, the temperature of the crystals or of the capacities connected in the circuit containing the crystals is varied inside certain limits by a 'regulable electrical heating element. Inasmuch as electrical heating, as well known in the art, is variable in very fine and safe manner, this manner of heating insures as a result a delicate and reliable regulation of the frequency and of the signal wobbling.

The invention is particularly important in connection with wobbling actions produced and needed in secret telephony, for in this case the wobbling signal frequency is rather low (1 to 2 periods per second). For heating-it is then possible to use an alternating current of any suitably low frequency so that the wobbling frequency is equal to the frequency of the alternating current,

while the wobble itself depends upon the amplitude of the alternating current or is proportional thereto.

It is advisable to choose the apparatus employed to govern the frequency such as the .condensers, piezo-electric crystals, etc., so that they will respond markedly to temperature variations.

For instance, if frequency variations of the signals are to be produced by the variation of the temperature of a. piezo-electric crystal, then a crystal polished (cut) along the electrical axis is used, for such a crystal is about three times as responsive to temperature changes as one out along the longitudinal axis. 1

But 'if frequency change is to be attained by changes of the capacity or the temperature of a could be influenced'by temperature variations;

to accomplish this all that is necessary is that the temperature variations should come to act upon both, i. e., on the crystal as well as the capacities in the same sense.

The application of this idea shall be explained 5 in more detail in what follows by referring to the drawing wherein:

Figures 1 and 2 illustrate known crystal and condenser circuit arrangements for purposes ofv explanation;

Figures 3 to 7 show variousvcondensers constructed in accordance with the present invention wherein the capacity is arranged to decrease with increase in heating; and

Figure 8 illustrates a condenser inaccordance 15 with the present invention whose capacity in?- creases with increase in heating.

A condenser such as indicated by B in Figure 1, as is well known, acts in a frequency raising sense in a crystal circuit when included in the latter in series with the crystal A, while a condenser connected in parallel to the crystal A, as is shown in Figure 2,'on the contrary, acts in the sense of a frequency reduction. The consequence is thatin both instances a capacity reduction of the condenser occasions a rise in the period of the crystal circuit, and a capacity increase on the contrary causes a diminution of the frequency in the crystal circuit. Hence, when using crystals whose natural period grows with the temperature, and if such rise in frequency is to be intensified by acting upon the condensers, the latter should be so designed that the capacity thereof will fall with the temperature. But when using crystals whose frequency decreases with the temperature (such as crystals which have been cut out of the mother quartz at right angles to the electrical axis), then for promoting or reinforcing this action recourse must be had to condensers whose capacity grows with the tem- 0 perature.

In Fig. 3 there is shown a double-walled casing i or jacketedglass vessel, preferably-cylindrical in shape. Within the glass vessel is a good conducting liquid or fluid 2, for example, mercury. Located above the conductive fluid 2 there is arranged an electrical heating element 3 which is confined within the space A of the doublewalled vessel. Connected to the heating element is a suitable machine 5 for supplying the heating current, for example, an alternating current generator. The outside of both double walls of the vessel i are coated with a conductive medium 6 and i such as tinfoil, copper, or the like. The central portion of the inner wall of the vessel is The operation of the arrangement Figure 3 is as follows:

If the air pressure inside space 4 is equal to the atmospheric pressure acting upon the mercury in the central tube 8, then the mercury columns in both spaces are at the same height or level. But when the heater 3 is heated by the electric current, then the pressure will be caused, to rise and the mercury will fall inside the space 4. As can be seen, this has the result that the capacity between the mercury 2 and the coats 6 and 1, i. e., between or across the terminals 9 and II) will diminish.-

As can be seen from Figure 3 the mercury inside tube 8 will rise when the mercury sinks in space 4. Such rise of the mercury in the central tube 8, therefore, acts against the sinking of the mercury inside space 4 and thus also against the real purpose of the scheme. In order to obviate this it is possible either to make the tube 8 throughout its entire length rather wide or else, as shown by the arrangement in Fig. 4, a better scheme wherein in order to save mercury, the tube 8 is made narrow and widened out only at its top end to form a receiver l I.

Fig. illustrates a modification wherein the inner tube could be dispensed with entirely and still prevent substantial rise in the inner space by designing the condenser with a central reservoir I 2, fiuid communication between the outer wall is maintained by the opening I3.

In the arrangements as shown in Figures 3 to 5, as will be understood, the capacity of the condenser is dependent upon atmospheric pressure of the outer space. In order to obviate this, as shown in Figure 6, the inside of the condenser may be shut off entirely and sealed from the outside atmosphere by a cover l4 and a suitable seal l5, as far as possible, so that the pressure in the interior of the condenser can be regulated at will.

Figure 7 is a modification similar to that of Fig. 6 except that in order that temperature changes outside of space 4 may produce no efiects upon the temperature of the interior portion, space 4 is separated from the interior portion by means of an additional partition I6 forming an air space l1.

The arrangement shown in Figure 8 diners from the one Figure '7 only in that a heating element I8 is provided in the interior portion rather than in space 4. As a result, in the case of an arrangement as in Figure 8, with growth of temperature in the interior portion the mercury will rise in space 4 with the consequence that the capacity grows.

Instead of an alternating current heating supply source, a direct current source could be employed for heating, though to less advantage, the intensity of the direct current being regulated periodically by some mechanical means.

The frequency of the crystal circuit could be varied also by that, for instance, in Figures 1 and 2 instead of the capacities or in combination therewith, variable inductances (variometers) are provided. The effect of a variometer is the opposite of that of a condenser. An ordinary coil, as is well known, is varied in a way so that it grows with growth of temperature. Hence, the purpose and end of this invention may also be realizable by using inductances in a. suitable manner.

I claim:

1. A variable condenser comprising a doublewalled vessel the walls of which define an annular space, a liquid within said vessel, a heater winding within the walls of said vessel, but not in electrical contact with said liquid, a source of energy for said winding, a pair of terminals for said condenser associated with the walls of said vessel whereby a rise or fall of said liquid varies the capacity between said terminals.

2. A variable condenser as defined in claim 1 characterized in this, that said liquid is mercury.

3. A variable reactance device comprising a. double-walled vessel the walls of which define an annular space, a quantity of mercury within said vessel, a heater winding within the walls of said vessel, but not in electrical contact with said liquid, a source of energy for said winding, a pair of terminals associated with the walls of said device whereby a rise or fall of said liquid varies the reactance of said device.

4. A variable condenser comprising a doublewalled vessel the walls of which define an annular space, a liquid within said vessel, a heating winding within the double walls of said vessel but not in contact with said liquid, a source of energy for said winding, a metallic coating acting as a condenser electrode partially surrounding the double walls of said vessel, the other electrode of said condenser comprising said liquid whereby the rise or fall of said liquid varies the capacity between the electrodes.

5. A variable condenser comprising a doublewalled vessel the-walls of which define an annular space, said vessel having a central tube arranged to be in liquid communication with said double walls, a liquid contained within said vessel, a heating winding within the double walls of said vessel but not in contact with said liquid, a source of energy for said winding, a metallic coating acting as a condenser electrode partially surrounding the double walls of said vessel, the other electrode of said condenser comprising said liquid whereby the rise or fall of said liquid varies the capacity between the electrodes.

6. A variable condenser comprising a doublewalled vessel the walls of which define an annular space, said vessel having a central reservoir arranged to be in liquid communication with said double walls, a liquid contained within said vessel, a heating winding within said double walls of said vessel but not in contact with said liquid, a source of energy for said winding, a metallic coating acting as a condenser electrode partially surrounding the double walls of said vessel, the other electrode of said condenser comprising said liquid whereby the rise or fall of said liquid varies the capacity between said electrodes.

7. A variable condenser comprising a doublewalled vessel the walls of which define an annular space, said vessel having a central reservoir arranged to be in liquid communication with said double walls, a cover for said vessel, said walled vessel the walls of which define an annular space, said vessel having a central reservoir arranged to be in liquid communication with said double walls, a cover for said vessel, said cover having a seal to exclude the outside atmosphere, a partition forming an air space between said double walls and said reservoir, a liquid contained within said vessel, a heating winding within said double walls of said vessel but not in contact with said liquid, a source of energy for said winding, a metallic coating acting as a condenser electrode partially surrounding the double walls of said vessel, the other electrode of said condenser com prising said liquid whereby the rise or fall of said liquid varies the capacity between said electrodes.

9. A variable condenser comprising a doublewalled vessel the walls of which define an annular space, said vessel having a central reservoir arranged to be in liquid communication with said double walls, a cover for said vessel, said cover having a seal to exclude the outside atmosphere, a partition forming an air space between said double walls and said reservoir, a liquid contained within said vessel, a heating element confined within the central portion of said reservoir but not in contact with said liquid, a source of energy for said winding, a metalliccoating acting as a condenser electrode partially sur-- rounding the double walls of said vessel, the other electrode of said condenser comprising said liquid whereby the rise or fall of said liquidvaries the capacity between said electrodes.

MENDEL OSN OS. 

